I’ve done a bit of looking around and there doesn’t seem to have been any festival other than the Kronia dedicated to one of the Titans. OTOH, that also depends on exactly how one defines “Titan”. To be sure, if you limit Titan to mean one of the twelve children of Ouranos—Kronos, Hyperion, etc.—then Kronos is the only one so honored. There were, however, several non-Olympians who had fesivals, many of them with Titanic connections.

First of all, there were Hekate and Selene, both daughters of the Titans; the last day of every month was sacred to Hekate and the first and fifteenth days of every month (the first visible crescent after the new moon and the full moon) were sacred to Selene. None of these was an actual festival, though.

More interesting is Selene’s brother Helios. He is often referred to by the poets as “Titan Helios” and Homer refers to his father, the Titan Hyperion, as Helios. The Pyanepsia (seventh Pyanepsion) was primarily a festival for Apollo, but both Helios and the Horai were also honored. The priest of Helios also played an important role in the Skirophoria, a festival which included some preliminary events for the Eleusinian mysteries, and the participants swore by Helios. It should also be noted that the Athenians considered themselves the children of the sun and earth (Phoibos and Ge).

There is one other who had a festival celebrated at Athens and, while usually considered an Olympian, could also be counted as one of the generation of the Titans: Aphrodite. There was an older myth of her birth that connected her to the oldest gods and made her the youngest sister of the Titans. It was said that when Kronos rebelled against his father Ouranos and cut off the latter’s genitals with his scythe, either blood or semen dripped from them and fell into the sea, where Aphrodite was engendered on the sea-foam. Still, she too was usually counted as an Olympan.

So it seems that Kronos was the only Titan given his own festival in the Attic calendar, although there were a number of festivals with pre-Olympian roots. It is also interesting to note the strong similarities between the Kronia and the Roman Saturnalia: both were festivals of license and inversion. Maybe the Romans got that from the Greeks in southern Italy or maybe it goes back much further.